JSF  provides a set of standard classes and associated tags that page authors and application developers can use to validate a component’s data. The Validator classes in JSF are:

• BeanValidator – Registers a bean validator for the component.
• DoubleRangeValidator -Checks whether the local value of a component is within a certain range
• LengthValidator – Checks whether the length of a component’s local value is within a certain range. The value must be a java.lang.String.
• LongRangeValidator -Checks whether the local value of a component is within a certain range.
• RegexValidator -Checks whether the local value of a component is a match against a regular expression from the java.util.regex package.
• RequiredValidator -Ensures that the local value is not empty on an javax.faces.component.EditableValueHolder component.

All these validator classes implement the javax.faces.validator.Validator interface. Custom validators can be created by implementing this interface.